By such a circular knitting machine which is disclosed in WO 2007/113659 the cam means is provided with a large number of cams having a fixed position in the circular knitting machine. A selection device is being used for moving a heel of a needle from an active position in which the heel will follow a retraction cam to an inactive position in which the heel of the needle will not follow the retraction cam but will pass along the retraction cam. If the retraction cam is being followed, the needle must pass all the fixed cams like extraction cams, knockover cams, central cams and complementary cams.
This renders the known circular knitting machine rather inflexible. Furthermore, the needles will follow a number of cams wherein the axial movement of the needles due to the cams does not contribute to the knitting process.